This present invention relates to contrast agent imaging. In particular, the cubic fundamental response provides agent specific ultrasound imaging.
Information at the cubic fundamental is detected by varying the transmit amplitude and phase associated with combined echo signals. Some techniques for detecting cubic fundamental information are disclosed in U.S. Pat. Nos. 6,494,841, 6,602,195, 6,632,177 and 6,682,482, the disclosures of which are incorporated herein by reference. The cubic fundamental information is highly specific to ultrasound contrast agents since contrast agents produce cubic response and the transducer and tissue produce very little cubic response. The information provides tissue clutter rejection, allowing for imaging more specific to contrast agents. For example, small vessels within tissue may be more easily imaged or identified using cubic fundamental information.
U.S. Pat. No. 6,638,228, the disclosure of which is incorporated herein by reference, provides for contrast-agent enhanced color-flow imaging. Power modulation or amplitude variation of the transmit pulses is used to obtain cubic fundamental information. A color Doppler estimator is used to detect the cubic fundamental information for imaging.